This invention relates to compositions for curing epoxide resins, to curable mixtures of these compositions and epoxide resins, and to cured products obtained by curing the aforesaid mixtures.
It is known that epoxide resins, i.e., substances containing on average more than one 1,2-epoxide group per molecule, may be cured by reaction with various classes of substances to form cross-linked, infusible, insoluble products having valuable technical properties. Typical curing agents include polyamines.
These are useful curing agents, and may be employed to cure epoxide resins at room temperature or at elevated temperatures. They suffer from the drawback, however, that curing commences as soon as they are mixed with the epoxide resin and so it is not possible to make `one shot` mixtures, i.e., mixtures of epoxide resins and such hardeners which remain stable on storage until required for use.
British Patent Specification No. 867,487 describes compounds prepared by the reaction of at least one epoxide group and a silicon-nitrogen compound (a `silamine`), itself prepared by reaction of a halosilane with ammonia or a primary amine. Suitable halosilanes used in the reaction are of the generic formula EQU R.sub.p --Si--Hal.sub.4-p I
where R represents a hydrogen atom or an organic group, and p is 1, 2, or 3. Suitable amines include methylamine, ethylamine, allylamine, ethylenediamine, hexamethylenediamine, aniline, p-phenylenediamine, and benzylamine. It is stated that silamines will cure epoxide resins at room temperature and that silamines made from primary amines tend to react with epoxy resins somewhat more rapidly than silamines derived from ammonia. The combination of epoxy resin and silamine has an exceedingly short `shelf-life` it is said, and the components are mixed only immediately before use. However, it is further stated that certain of the silamines may be used as curing agents for epoxide resins wherein the mixture of curing agent and resin has a shelf-life of days or weeks. From what is stated previously it is implied that these less-active silamines are those derived from ammonia.
That specification gives no example of a silamine prepared from a monohalosilane and no example of a silamine prepared from a diamine although such are included within the general description. Further, that specification indicates that no mixture of an epoxide and a silamine would be stable for longer than a few weeks.
We have now found that combinations of epoxide resins with silamines derived from a monohalosilane and a di- or polyamine, the said combinations further containing a substantially anhydrous organic acid or phenol, are stable in the absence of moisture for several months at room temperatures and at elevated temperatures up to about 80.degree. C. Such combinations will then cure rapidly at room temperature or elevated temperature when exposed to water or water vapour. These combinations therefore form a storage-stable but rapidly-curing `one-shot` epoxide resin composition.